Kinetic studies on the dimerization of isobutene with Ni/Al2O3 as a catalyst for reactive distillation process

Isooctane is a promising gasoline additive that could be produced by dimerization of isobutene (IB) with subsequent hydrogenation. In this work, the dimerization of IB has been carried out in a batch reactor over a temperature range of 338–383 K in the presence of laboratory prepared Ni/Al2O3 as a catalyst and n-pentane as solvent. The influence of various parameters such as temperature, catalyst loading and initial concentration of IB was examined. A Langmuir–Hinshelwood kinetic model of IB dimerization was established and the parameters were estimated on the basis of the measured data. The feasibility of oligomerization of IB based on the reactive distillation was simulated in ASPEN PLUS using the kinetics developed. The simulation results showed that the catalyst of Ni/Al2O3 had higher selectivity to diisobutene (DIB) and slightly lower conversion of IB than ion exchange resin in the absence of polar substances.

Graphical AbstractA kinetic model of IB dimerization with Ni/Al2O3 as the catalyst was developed in this work. The kinetics was applied to simulate the process of IB dimerization in RD. Simulation results show that the concentration of DIB in the reactive zone is maintained at a relatively low level, which suppresses the formation of TIB and higher oligomers. High purity of DIB (> 0.86) can be acquired as the bottom product. Meanwhile, the conversion of IB is 98.84% and the selectivity to DIB is 84.91% which is higher than ion exchange resin as a catalyst in the same condition.Figure optionsDownload as PowerPoint slide